Evidence has been presented to indicate that two strains of obese mice (ob/ob and NZO) respond to treatment with pancreatic polypeptide (PP) by reduction in rate of weight gain and in rate of food consumption. This project proposes to measure PP in pancreas and in blood of obese mice in order to learn if PP deficiency exists in these animals. Murine PP does not cross react well with existing anti-PP serum eg. bovine, human or avian and, therefore, rat PP is being isolated. This will be used to develop an immunoassay for murine PP which will be applied to an immunocytochemical study of mouse pancreatic islets, using both obese and lean mice. In addition, plasma PP levels will be estimated in lean and obese mice in order to compare PP secretory mechanisms in the two groups of mice. Amino acid sequence studies will be performed on rat PP.